The present invention relates to a laminated printed coil structure suitable for a motor coil of a compact motor, for example.
Conventionally, there has been proposed a laminated printed coil structure for a motor coil of a compact motor, for example, which structure is formed by laminating a plurality of sheets on which coil patterns are formed and disposing such laminated sheets on a printed wiring board.
Referring to FIG. 4 which shows an example of the conventional laminated print coil structure, reference numerals 1, 2 and 3 designate sheets, on both sides of each of which coil patterns 7 are formed. The sheets 1, 2 and 3 are bonded to one another. One end of each of the coil patterns 7 is connected to terminals la, 2a and 3a, while the respective other end is connected to terminals lb, 2b and 3b.
The sheets 1, 2, and 3 as laminated are bonded to a printed wiring board 4. The terminals 1a, 2a and 3a are connected to a predetermined wiring pattern of the wiring board 4, which patterns are led out to terminals 4A, 4B, and 4C. The terminals 1a, 2b and 3b are connected to a common predetermined wiring pattern of the wiring board 4, which pattern is led out to a terminal 4D.
The prior laminated printed coil structure is produced as shown in FIGS. 5A to 5C, for example. First, as shown in FIG. 5A, the sheets 1, 2 and 3 having the respective coil patterns are prepared. Then, as shown in FIG. 5B, the sheets 1, 2 and 3 are bonded to one another by means of adhesive sheets (not shown). Then, as shown in FIG. 5C, the laminated sheets 1, 2 and 3 are bonded to the printed wiring board 4 by means of an adhesive sheets (not shown). Finally, the terminals 1a to 3a and 1b to 3b are connected to predetermined wiring patterns 4a to 4d of the wiring board 4 by soldering or the like.
In the conventional laminated print coil structure shown in FIG. 4, there is defined almost no gap between the terminal 3a and the wiring pattern 4C of the wiring board 4, for example. Therefore, in the case that the terminal 3a is connected to the wiring pattern 4c by means of a conductive paste, reliability of connection is not satisfactory. As shown in FIG. 6A, a conductive paste 5 is interposed between the terminal 3a and the wiring pattern 4c. Then, the terminal 3a and the wiring pattern 4c are pressed to be connected with each other as shown in FIG. 6B. However, the conductive paste 5 flows out as shown by arrows, thus reducing the reliability of connection.
Furthermore, in the prior art shown in FIG. 4, there is defined a large gap between the terminal 1a and the wiring pattern 4a of the wiring board 4, for example. Therefore, in the case that the terminal la is connected to the wiring pattern 4a by soldering paste printing and subsequent reflowing, there is a possibility that the connection between the terminal 1a and the wiring pattern 4a is not attained because of shrinkage of the soldering paste. As shown in FIG. 7A, a soldering paste 7 is interposed between the terminal la and the wiring pattern 4a. When reflowing is carried out in the soldering paste 6 under the large gap condition, the soldering paste 6 may shrink into disconnection between the terminal 1a and the wiring pattern 4a as shown in FIG. 7B.
Accordingly, the terminals 1a to 3a and 1b to 3b are connected to the predetermined wiring patterns of the wiring board 4 by a manual soldering work, for example. However, even in the manual soldering effort, the soldering paste is difficult to apply at a large-gapped portion, thus reducing reliability of the soldering step.